css: update color for code highlighter
css: update color for code highlighter

ArthurChiao/arthurchiao.github.io,ArthurChiao/arthurchiao.github.io,ArthurChiao/arthurchiao.github.io,ArthurChiao/arthurchiao.github.io,ArthurChiao/arthurchiao.github.io,ArthurChiao/arthurchiao.github.io